path: root/src/mesa/drivers/dri/r128/r128_texstate.c

/**************************************************************************

Copyright 1999, 2000 ATI Technologies Inc. and Precision Insight, Inc.,
                                               Cedar Park, Texas.
All Rights Reserved.

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
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the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice (including the next
paragraph) shall be included in all copies or substantial portions of the
Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
ATI, PRECISION INSIGHT AND/OR THEIR SUPPLIERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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**************************************************************************/

/*
 * Authors:
 *   Gareth Hughes <gareth@valinux.com>
 *   Kevin E. Martin <martin@valinux.com>
 *   Brian Paul <brianp@valinux.com>
 */

#include "main/glheader.h"
#include "main/imports.h"
#include "main/context.h"
#include "main/macros.h"

#include "r128_context.h"
#include "r128_ioctl.h"
#include "r128_tris.h"
#include "r128_tex.h"


static void r128SetTexImages( r128ContextPtr rmesa,
                              const struct gl_texture_object *tObj )
{
   r128TexObjPtr t = (r128TexObjPtr) tObj->DriverData;
   struct gl_texture_image *baseImage = tObj->Image[0][tObj->BaseLevel];
   int log2Pitch, log2Height, log2Size, log2MinSize;
   int totalSize;
   int i;
   GLint firstLevel, lastLevel;

   assert(t);
   assert(baseImage);

   if ( R128_DEBUG & DEBUG_VERBOSE_API )
      fprintf( stderr, "%s( %p )\n", __FUNCTION__, (void *) tObj );

   switch (baseImage->TexFormat) {
   case MESA_FORMAT_ARGB8888:
   case MESA_FORMAT_ARGB8888_REV:
      t->textureFormat = R128_DATATYPE_ARGB8888;
      break;
   case MESA_FORMAT_ARGB4444:
   case MESA_FORMAT_ARGB4444_REV:
      t->textureFormat = R128_DATATYPE_ARGB4444;
      break;
   case MESA_FORMAT_RGB565:
   case MESA_FORMAT_RGB565_REV:
      t->textureFormat = R128_DATATYPE_RGB565;
      break;
   case MESA_FORMAT_RGB332:
      t->textureFormat = R128_DATATYPE_RGB8;
      break;
   case MESA_FORMAT_CI8:
      t->textureFormat = R128_DATATYPE_CI8;
      break;
   case MESA_FORMAT_YCBCR:
      t->textureFormat = R128_DATATYPE_YVYU422;
      break;
   case MESA_FORMAT_YCBCR_REV:
      t->textureFormat = R128_DATATYPE_VYUY422;
      break;
   default:
      _mesa_problem(rmesa->glCtx, "Bad texture format in %s", __FUNCTION__);
   };

   /* Compute which mipmap levels we really want to send to the hardware.
    */

   driCalculateTextureFirstLastLevel( (driTextureObject *) t );
   firstLevel = t->base.firstLevel;
   lastLevel  = t->base.lastLevel;

   log2Pitch = tObj->Image[0][firstLevel]->WidthLog2;
   log2Height = tObj->Image[0][firstLevel]->HeightLog2;
   log2Size = MAX2(log2Pitch, log2Height);
   log2MinSize = log2Size;

   t->base.dirty_images[0] = 0;
   totalSize = 0;
   for ( i = firstLevel; i <= lastLevel; i++ ) {
      const struct gl_texture_image *texImage;

      texImage = tObj->Image[0][i];
      if ( !texImage || !texImage->Data ) {
         lastLevel = i - 1;
	 break;
      }

      log2MinSize = texImage->MaxLog2;

      t->image[i - firstLevel].offset = totalSize;
      t->image[i - firstLevel].width  = tObj->Image[0][i]->Width;
      t->image[i - firstLevel].height = tObj->Image[0][i]->Height;

      t->base.dirty_images[0] |= (1 << i);

      totalSize += (tObj->Image[0][i]->Height *
		    tObj->Image[0][i]->Width *
		    _mesa_get_format_bytes(tObj->Image[0][i]->TexFormat));

      /* Offsets must be 32-byte aligned for host data blits and tiling */
      totalSize = (totalSize + 31) & ~31;
   }

   t->base.totalSize = totalSize;
   t->base.firstLevel = firstLevel;
   t->base.lastLevel = lastLevel;

   /* Set the texture format */
   t->setup.tex_cntl &= ~(0xf << 16);
   t->setup.tex_cntl |= t->textureFormat;

   t->setup.tex_combine_cntl = 0x00000000;  /* XXX is this right? */

   t->setup.tex_size_pitch = ((log2Pitch   << R128_TEX_PITCH_SHIFT) |
			      (log2Size    << R128_TEX_SIZE_SHIFT) |
			      (log2Height  << R128_TEX_HEIGHT_SHIFT) |
			      (log2MinSize << R128_TEX_MIN_SIZE_SHIFT));

   for ( i = 0 ; i < R128_MAX_TEXTURE_LEVELS ; i++ ) {
      t->setup.tex_offset[i]  = 0x00000000;
   }

   if (firstLevel == lastLevel)
      t->setup.tex_cntl |= R128_MIP_MAP_DISABLE;
   else
      t->setup.tex_cntl &= ~R128_MIP_MAP_DISABLE;

   /* FYI: r128UploadTexImages( rmesa, t ); used to be called here */
}


/* ================================================================
 * Texture combine functions
 */

#define COLOR_COMB_DISABLE		(R128_COMB_DIS |		\
					 R128_COLOR_FACTOR_TEX)
#define COLOR_COMB_COPY_INPUT		(R128_COMB_COPY_INP |		\
					 R128_COLOR_FACTOR_TEX)
#define COLOR_COMB_MODULATE		(R128_COMB_MODULATE |		\
					 R128_COLOR_FACTOR_TEX)
#define COLOR_COMB_MODULATE_NTEX	(R128_COMB_MODULATE |		\
					 R128_COLOR_FACTOR_NTEX)
#define COLOR_COMB_ADD			(R128_COMB_ADD |		\
					 R128_COLOR_FACTOR_TEX)
#define COLOR_COMB_BLEND_TEX		(R128_COMB_BLEND_TEXTURE |	\
					 R128_COLOR_FACTOR_TEX)
/* Rage 128 Pro/M3 only! */
#define COLOR_COMB_BLEND_COLOR		(R128_COMB_MODULATE2X |		\
					 R128_COMB_FCN_MSB |		\
					 R128_COLOR_FACTOR_CONST_COLOR)

#define ALPHA_COMB_DISABLE		(R128_COMB_ALPHA_DIS |		\
					 R128_ALPHA_FACTOR_TEX_ALPHA)
#define ALPHA_COMB_COPY_INPUT		(R128_COMB_ALPHA_COPY_INP |	\
					 R128_ALPHA_FACTOR_TEX_ALPHA)
#define ALPHA_COMB_MODULATE		(R128_COMB_ALPHA_MODULATE |	\
					 R128_ALPHA_FACTOR_TEX_ALPHA)
#define ALPHA_COMB_MODULATE_NTEX	(R128_COMB_ALPHA_MODULATE |	\
					 R128_ALPHA_FACTOR_NTEX_ALPHA)
#define ALPHA_COMB_ADD			(R128_COMB_ALPHA_ADD |		\
					 R128_ALPHA_FACTOR_TEX_ALPHA)

#define INPUT_INTERP			(R128_INPUT_FACTOR_INT_COLOR |	\
					 R128_INP_FACTOR_A_INT_ALPHA)
#define INPUT_PREVIOUS			(R128_INPUT_FACTOR_PREV_COLOR |	\
					 R128_INP_FACTOR_A_PREV_ALPHA)

static GLboolean r128UpdateTextureEnv( struct gl_context *ctx, int unit )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);
   GLint source = rmesa->tmu_source[unit];
   const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[source];
   const struct gl_texture_object *tObj = texUnit->_Current;
   const GLenum format = tObj->Image[0][tObj->BaseLevel]->_BaseFormat;
   GLuint combine;

   if ( R128_DEBUG & DEBUG_VERBOSE_API ) {
      fprintf( stderr, "%s( %p, %d )\n",
	       __FUNCTION__, (void *) ctx, unit );
   }

   if ( unit == 0 ) {
      combine = INPUT_INTERP;
   } else {
      combine = INPUT_PREVIOUS;
   }

   /* Set the texture environment state */
   switch ( texUnit->EnvMode ) {
   case GL_REPLACE:
      switch ( format ) {
      case GL_RGBA:
      case GL_LUMINANCE_ALPHA:
      case GL_INTENSITY:
	 combine |= (COLOR_COMB_DISABLE |		/* C = Ct            */
		     ALPHA_COMB_DISABLE);		/* A = At            */
	 break;
      case GL_RGB:
      case GL_LUMINANCE:
	 combine |= (COLOR_COMB_DISABLE |		/* C = Ct            */
		     ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 break;
      case GL_ALPHA:
	 combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
		     ALPHA_COMB_DISABLE);		/* A = At            */
	 break;
      case GL_COLOR_INDEX:
      default:
	 return GL_FALSE;
      }
      break;

   case GL_MODULATE:
      switch ( format ) {
      case GL_RGBA:
      case GL_LUMINANCE_ALPHA:
      case GL_INTENSITY:
	 combine |= (COLOR_COMB_MODULATE |		/* C = CfCt          */
		     ALPHA_COMB_MODULATE);		/* A = AfAt          */
	 break;
      case GL_RGB:
      case GL_LUMINANCE:
	 combine |= (COLOR_COMB_MODULATE |		/* C = CfCt          */
		     ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 break;
      case GL_ALPHA:
	 combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
		     ALPHA_COMB_MODULATE);		/* A = AfAt          */
	 break;
      case GL_COLOR_INDEX:
      default:
	 return GL_FALSE;
      }
      break;

   case GL_DECAL:
      switch ( format ) {
      case GL_RGBA:
	 combine |= (COLOR_COMB_BLEND_TEX |		/* C = Cf(1-At)+CtAt */
		     ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 break;
      case GL_RGB:
	 combine |= (COLOR_COMB_DISABLE |		/* C = Ct            */
		     ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 break;
      case GL_ALPHA:
      case GL_LUMINANCE:
      case GL_LUMINANCE_ALPHA:
      case GL_INTENSITY:
	 /* Undefined behaviour - just copy the incoming fragment */
	 combine |= (COLOR_COMB_COPY_INPUT |		/* C = undefined     */
		     ALPHA_COMB_COPY_INPUT);		/* A = undefined     */
	 break;
      case GL_COLOR_INDEX:
      default:
	 return GL_FALSE;
      }
      break;

   case GL_BLEND:
      /* Rage 128 Pro and M3 can handle GL_BLEND texturing.
       */
      if ( !R128_IS_PLAIN( rmesa ) ) {
         /* XXX this hasn't been fully tested, I don't have a Pro card. -BP */
	 switch ( format ) {
	 case GL_RGBA:
	 case GL_LUMINANCE_ALPHA:
	    combine |= (COLOR_COMB_BLEND_COLOR |	/* C = Cf(1-Ct)+CcCt */
			ALPHA_COMB_MODULATE);		/* A = AfAt          */
	    break;

	 case GL_RGB:
	 case GL_LUMINANCE:
	    combine |= (COLOR_COMB_BLEND_COLOR |	/* C = Cf(1-Ct)+CcCt */
			ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	    break;

	 case GL_ALPHA:
	    combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
			ALPHA_COMB_MODULATE);		/* A = AfAt          */
	    break;

	 case GL_INTENSITY:
	    /* GH: We could be smarter about this... */
	    switch ( rmesa->env_color & 0xff000000 ) {
	    case 0x00000000:
	       combine |= (COLOR_COMB_BLEND_COLOR |	/* C = Cf(1-It)+CcIt */
			   ALPHA_COMB_MODULATE_NTEX);	/* A = Af(1-It)      */
	    default:
	       combine |= (COLOR_COMB_MODULATE |	/* C = fallback      */
			   ALPHA_COMB_MODULATE);	/* A = fallback      */
	       return GL_FALSE;
	    }
	    break;

	 case GL_COLOR_INDEX:
	 default:
	    return GL_FALSE;
	 }
	 break;
      }

      /* Rage 128 has to fake some cases of GL_BLEND, otherwise fallback
       * to software rendering.
       */
      if ( rmesa->blend_flags ) {
	 return GL_FALSE;
      }
      switch ( format ) {
      case GL_RGBA:
      case GL_LUMINANCE_ALPHA:
	 switch ( rmesa->env_color & 0x00ffffff ) {
	 case 0x00000000:
	    combine |= (COLOR_COMB_MODULATE_NTEX |	/* C = Cf(1-Ct)      */
			ALPHA_COMB_MODULATE);		/* A = AfAt          */
	    break;
#if 0
         /* This isn't right - BP */
	 case 0x00ffffff:
	    if ( unit == 0 ) {
	       combine |= (COLOR_COMB_MODULATE_NTEX |	/* C = Cf(1-Ct)      */
			   ALPHA_COMB_MODULATE);	/* A = AfAt          */
	    } else {
	       combine |= (COLOR_COMB_ADD |		/* C = Cf+Ct         */
			   ALPHA_COMB_COPY_INPUT);	/* A = Af            */
	    }
	    break;
#endif
	 default:
	    combine |= (COLOR_COMB_MODULATE |		/* C = fallback      */
			ALPHA_COMB_MODULATE);		/* A = fallback      */
	    return GL_FALSE;
	 }
	 break;
      case GL_RGB:
      case GL_LUMINANCE:
	 switch ( rmesa->env_color & 0x00ffffff ) {
	 case 0x00000000:
	    combine |= (COLOR_COMB_MODULATE_NTEX |	/* C = Cf(1-Ct)      */
			ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	    break;
#if 0
         /* This isn't right - BP */
	 case 0x00ffffff:
	    if ( unit == 0 ) {
	       combine |= (COLOR_COMB_MODULATE_NTEX |	/* C = Cf(1-Ct)      */
			   ALPHA_COMB_COPY_INPUT);	/* A = Af            */
	    } else {
	       combine |= (COLOR_COMB_ADD |		/* C = Cf+Ct         */
			   ALPHA_COMB_COPY_INPUT);	/* A = Af            */
	    }
	    break;
#endif
	 default:
	    combine |= (COLOR_COMB_MODULATE |		/* C = fallback      */
			ALPHA_COMB_COPY_INPUT);		/* A = fallback      */
	    return GL_FALSE;
	 }
	 break;
      case GL_ALPHA:
	 if ( unit == 0 ) {
	    combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
			ALPHA_COMB_MODULATE);		/* A = AfAt          */
	 } else {
	    combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
			ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 }
	 break;
      case GL_INTENSITY:
	 switch ( rmesa->env_color & 0x00ffffff ) {
	 case 0x00000000:
	    combine |= COLOR_COMB_MODULATE_NTEX;	/* C = Cf(1-It)      */
	    break;
#if 0
         /* This isn't right - BP */
	 case 0x00ffffff:
	    if ( unit == 0 ) {
	       combine |= COLOR_COMB_MODULATE_NTEX;	/* C = Cf(1-It)      */
	    } else {
	       combine |= COLOR_COMB_ADD;		/* C = Cf+It         */
	    }
	    break;
#endif
	 default:
	    combine |= (COLOR_COMB_MODULATE |		/* C = fallback      */
			ALPHA_COMB_MODULATE);		/* A = fallback      */
	    return GL_FALSE;
	 }
	 switch ( rmesa->env_color & 0xff000000 ) {
	 case 0x00000000:
	    combine |= ALPHA_COMB_MODULATE_NTEX;	/* A = Af(1-It)      */
	    break;
#if 0
         /* This isn't right - BP */
	 case 0xff000000:
	    if ( unit == 0 ) {
	       combine |= ALPHA_COMB_MODULATE_NTEX;	/* A = Af(1-It)      */
	    } else {
	       combine |= ALPHA_COMB_ADD;		/* A = Af+It         */
	    }
	    break;
#endif
	 default:
	    combine |= (COLOR_COMB_MODULATE |		/* C = fallback      */
			ALPHA_COMB_MODULATE);		/* A = fallback      */
	    return GL_FALSE;
	 }
	 break;
      case GL_COLOR_INDEX:
      default:
	 return GL_FALSE;
      }
      break;

   case GL_ADD:
      switch ( format ) {
      case GL_RGBA:
      case GL_LUMINANCE_ALPHA:
	 combine |= (COLOR_COMB_ADD |			/* C = Cf+Ct         */
		     ALPHA_COMB_MODULATE);		/* A = AfAt          */
	 break;
      case GL_RGB:
      case GL_LUMINANCE:
	 combine |= (COLOR_COMB_ADD |			/* C = Cf+Ct         */
		     ALPHA_COMB_COPY_INPUT);		/* A = Af            */
	 break;
      case GL_ALPHA:
	 combine |= (COLOR_COMB_COPY_INPUT |		/* C = Cf            */
		     ALPHA_COMB_MODULATE);		/* A = AfAt          */
	 break;
      case GL_INTENSITY:
	 combine |= (COLOR_COMB_ADD |			/* C = Cf+Ct         */
		     ALPHA_COMB_ADD);			/* A = Af+At         */
	 break;
      case GL_COLOR_INDEX:
      default:
	 return GL_FALSE;
      }
      break;

   default:
      return GL_FALSE;
   }

   if ( rmesa->tex_combine[unit] != combine ) {
     rmesa->tex_combine[unit] = combine;
     rmesa->dirty |= R128_UPLOAD_TEX0 << unit;
   }
   return GL_TRUE;
}

static void disable_tex( struct gl_context *ctx, int unit )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);

   FLUSH_BATCH( rmesa );

   if ( rmesa->CurrentTexObj[unit] ) {
      rmesa->CurrentTexObj[unit]->base.bound &= ~(1 << unit);
      rmesa->CurrentTexObj[unit] = NULL;
   }

   rmesa->setup.tex_cntl_c &= ~(R128_TEXMAP_ENABLE << unit);
   rmesa->setup.tex_size_pitch_c &= ~(R128_TEX_SIZE_PITCH_MASK << 
				      (R128_SEC_TEX_SIZE_PITCH_SHIFT * unit));
   rmesa->dirty |= R128_UPLOAD_CONTEXT;

   /* If either texture unit is disabled, then multitexturing is not
    * happening.
    */

   rmesa->blend_flags &= ~R128_BLEND_MULTITEX;
}

static GLboolean enable_tex_2d( struct gl_context *ctx, int unit )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);
   const int source = rmesa->tmu_source[unit];
   const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[source];
   const struct gl_texture_object *tObj = texUnit->_Current;
   r128TexObjPtr t = (r128TexObjPtr) tObj->DriverData;

   /* Need to load the 2d images associated with this unit.
    */
   if ( t->base.dirty_images[0] ) {
      /* FIXME: For Radeon, RADEON_FIREVERTICES is called here.  Should
       * FIXME: something similar be done for R128?
       */
      /*  FLUSH_BATCH( rmesa ); */

      r128SetTexImages( rmesa, tObj );
      r128UploadTexImages( rmesa, t );
      if ( !t->base.memBlock ) 
	  return GL_FALSE;
   }

   return GL_TRUE;
}

static GLboolean update_tex_common( struct gl_context *ctx, int unit )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);
   const int source = rmesa->tmu_source[unit];
   const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[source];
   const struct gl_texture_object *tObj = texUnit->_Current;
   r128TexObjPtr t = (r128TexObjPtr) tObj->DriverData;


   /* Fallback if there's a texture border */
   if ( tObj->Image[0][tObj->BaseLevel]->Border > 0 ) {
      return GL_FALSE;
   }


   /* Update state if this is a different texture object to last
    * time.
    */
   if ( rmesa->CurrentTexObj[unit] != t ) {
      if ( rmesa->CurrentTexObj[unit] != NULL ) {
	 /* The old texture is no longer bound to this texture unit.
	  * Mark it as such.
	  */

	 rmesa->CurrentTexObj[unit]->base.bound &= 
	     ~(1UL << unit);
      }

      rmesa->CurrentTexObj[unit] = t;
      t->base.bound |= (1UL << unit);
      rmesa->dirty |= R128_UPLOAD_TEX0 << unit;

      driUpdateTextureLRU( (driTextureObject *) t ); /* XXX: should be locked! */
   }

   /* FIXME: We need to update the texture unit if any texture parameters have
    * changed, but this texture was already bound.  This could be changed to
    * work like the Radeon driver where the texture object has it's own
    * dirty state flags
    */
   rmesa->dirty |= R128_UPLOAD_TEX0 << unit;

   /* register setup */
   rmesa->setup.tex_size_pitch_c &= ~(R128_TEX_SIZE_PITCH_MASK << 
				      (R128_SEC_TEX_SIZE_PITCH_SHIFT * unit));

   if ( unit == 0 ) {
      rmesa->setup.tex_cntl_c       |= R128_TEXMAP_ENABLE;
      rmesa->setup.tex_size_pitch_c |= t->setup.tex_size_pitch << 0;
      rmesa->setup.scale_3d_cntl    &= ~R128_TEX_CACHE_SPLIT;
      t->setup.tex_cntl             &= ~R128_SEC_SELECT_SEC_ST;
   }
   else {
      rmesa->setup.tex_cntl_c       |= R128_SEC_TEXMAP_ENABLE;
      rmesa->setup.tex_size_pitch_c |= t->setup.tex_size_pitch << 16;
      rmesa->setup.scale_3d_cntl    |= R128_TEX_CACHE_SPLIT;
      t->setup.tex_cntl             |=  R128_SEC_SELECT_SEC_ST;

      /* If the second TMU is enabled, then multitexturing is happening.
       */
      if ( R128_IS_PLAIN( rmesa ) )
	  rmesa->blend_flags            |= R128_BLEND_MULTITEX;
   }

   rmesa->dirty |= R128_UPLOAD_CONTEXT;


   /* FIXME: The Radeon has some cached state so that it can avoid calling
    * FIXME: UpdateTextureEnv in some cases.  Is that possible here?
    */
   return r128UpdateTextureEnv( ctx, unit );
}

static GLboolean updateTextureUnit( struct gl_context *ctx, int unit )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);
   const int source = rmesa->tmu_source[unit];
   const struct gl_texture_unit *texUnit = &ctx->Texture.Unit[source];


   if (texUnit->_ReallyEnabled & (TEXTURE_1D_BIT | TEXTURE_2D_BIT)) {
      return (enable_tex_2d( ctx, unit ) &&
	      update_tex_common( ctx, unit ));
   }
   else if ( texUnit->_ReallyEnabled ) {
      return GL_FALSE;
   }
   else {
      disable_tex( ctx, unit );
      return GL_TRUE;
   }
}


void r128UpdateTextureState( struct gl_context *ctx )
{
   r128ContextPtr rmesa = R128_CONTEXT(ctx);
   GLboolean ok;


   /* This works around a quirk with the R128 hardware.  If only OpenGL 
    * TEXTURE1 is enabled, then the hardware TEXTURE0 must be used.  The
    * hardware TEXTURE1 can ONLY be used when hardware TEXTURE0 is also used.
    */

   rmesa->tmu_source[0] = 0;
   rmesa->tmu_source[1] = 1;

   if ((ctx->Texture._EnabledUnits & 0x03) == 0x02) {
      /* only texture 1 enabled */
      rmesa->tmu_source[0] = 1;
      rmesa->tmu_source[1] = 0;
   }

   ok = (updateTextureUnit( ctx, 0 ) &&
	 updateTextureUnit( ctx, 1 ));

   FALLBACK( rmesa, R128_FALLBACK_TEXTURE, !ok );
}